Device for moving and orienting spraying nozzles in a coating pan

ABSTRACT

A device moves and orients spraying nozzles ( 4 ) inside a coating pan ( 1 ). The spraying nozzles ( 4 ) are carried, arranged in a line, by a shaft ( 5 ), which rotates on a horizontal axis parallel to the axis of the rotating drum ( 1 ). The shaft ( 5 ) is supported by a support frame ( 7 ), which is fastened to a bar ( 10 ), which is rotated to adjust the distance between the spraying nozzles ( 4 ) and the free surface ( 20 ) of said mass of articles ( 2 ) being treated. The shaft ( 5 ) is fastened to the lever mechanism ( 16,17 ) of a positioning member ( 15 ) for changing the inclination of the spraying nozzles ( 4 ), so as to maintain constant their orientation with respect to said free surface ( 20 ) of the mass of articles ( 2 ).

FIELD OF THE INVENTION

The present invention relates to machines for coating granular articles,such as pharmaceutical or confectionery products, with an outer layer.

More precisely, the invention relates to a device for moving andorienting the spraying nozzles in a coating pan of a machine for coatinggranular articles.

DESCRIPTION OF THE PRIOR ART

Currently, articles to be treated are coated in machines including arotating drum, called coating pan, inside which the articles areintroduced.

The coating pan is equipped with perforated hollow bodies, which extendfrom a manifold coaxial with the rotating drum, and which are immersedin the moving mass of articles to be treated.

A suitable liquid mixture is sprayed on the articles through nozzles, soas to form a protective coating.

Afterwards, a flow of hot air is sent into the articles mass, so as todry the coating layer.

According to another use of the above mentioned machine, neutralgranules are coated with mixtures of active principles and excipients,so as to form e.g. controlled release medicine pellets.

In this case, a predetermined quantity of neutral granules areintroduced into the coating pan, so as to be covered, with help of asuitable binder, with layers of mixed powders containing activeprinciples, and excipients.

The binder is introduced into the rotating drum by the spraying nozzles.

During the drum rotation, the appearance of the mass of granulararticles changes in relation to different working parameters, e.g.rotation speed and physical characteristics of the articles, generallywith the free surface inclined with respect to a horizontal plane.

Therefore, adjusting the position of the spraying nozzlescorrespondingly to the articles position is a problem that isencountered.

Actually, it is known that best results are obtained when the sprayingnozzles are oriented substantially perpendicular to the free surface ofthe mass of the articles being coated, and at a predetermined distancetherefrom.

It is also to be noted that during the production cycle, the volume ofthe granular articles changes, usually increases, due to the coatinglayer which settles thereon.

Consequently, the position of the spraying nozzles must be changed inrelation to the changing position of the free surface of the granulararticles.

In known machines, the position of the spraying nozzles can usually beadjusted manually, with the machine stopped, by acting inside thecoating pan or after having removed the nozzles group therefrom.

It is obvious that such manual adjustment is not only difficult, butdoes not allow to intervene during the articles coating process.

This reduces considerably the efficiency of the coating process and doesnot allow to obtain best results in different situations.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the above problem byproposing a device which allows to move and locate the spraying nozzlesby acting from outside the coating pan and during the granular articlescoating process.

Another object of the present invention is to propose a device, which isvery versatile in relation to the kind of liquid substance to besprayed, and in particular, which can be used either for coatingpharmaceutical or confectionery products with an outer protective layer,or coating the neutral granules with mixtures of active principles andexcipients to obtain e.g. pharmaceutical pellets.

A further object of the present invention is to propose a device, whoseconstruction is very simple and functional.

The above mentioned objects are obtained, in accordance with the claims,by a device for moving and orienting spraying nozzles in a coating pan,the coating pan including:

a rotating drum rotated on a first rotation axis for mixing apredetermined mass of articles being coated, said mass of articledefining a free surface; and

a group of spraying nozzles situated inside said rotating drum forspraying a liquid mixture for coating said articles;

said device being characterized by:

a bar supported inside said rotating drum and protruding partiallyoutside said rotating drum;

a support frame, fastened to said bar and located inside said rotatingdrum;

a shaft rotatably supported by said support frame, said shaft being freeto rotate on a second rotation axis parallel to said first rotation axisof said rotating drum;

a plurality of spraying nozzles carried, arranged in a line, by saidshaft at a selected distance from said mass of articles being treatedwith a selected orientation with respect to said free surface of themass of articles;

a positioning member having a lever mechanism connected to said shaftfor changing inclination of said spraying nozzles and maintainingconstant the orientation of said spraying nozzles with respect to saidfree surface of the mass of articles;

said bar being rotated to adjust said distance between said sprayingnozzles and said free surface of said mass of articles being treated.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristic features of the present invention will be pointed outin the following description of a preferred, but not only embodiment,with reference to the enclosed drawings, in which:

FIG. 1 is a schematic longitudinal section view of a coating pan of amachine for coating particulate articles, equipped with the proposeddevice for moving and orienting of the spraying nozzles;

FIG. 2 is a cross-section view of the coating pan;

FIG. 2a is an enlarged view of a part of FIG. 2, to show better theproposed device for moving and orienting the spraying nozzles;

FIG. 3 is a lateral view of the device for moving and orienting thespraying nozzles;

FIGS. 3a and 3 b are views of an enlarged particular of the proposeddevice, indicated with K in FIG. 3, in different working steps.

BEST MODES OF CARRYING OUT THE INVENTION

With reference to the above figures, reference numeral 1 indicates arotating drum, or coating pan, which receives particulate articles 2 tobe treated.

The coating pan is formed e.g. by a central cylindrical part and twoterminal truncated cone parts.

The coating pan 1 is rotatably carried by a stationary framework 2. Therotational axis of the coating pan is horizontal, and its front partfeatures an opening 3 for introducing articles.

A tubular manifold, not shown for sake of clarity, is situated insidethe coating pan 1, substantially coaxial with the coating pan.

The tubular manifold communicates with an outer pipe, through which theair for drying the treated articles passes.

A pair of perforated hollow bodies, not shown, extend from the manifold,so as to be dipped into the moving mass of the articles to be treated.

A group of spraying nozzles 4 is situated inside the coating pan 4, soas to spray the liquid mixture onto the articles to form a coatinglayer.

The spraying nozzles 4 are carried, arranged in line one beside another,by a horizontal shaft 5, which passes through a sleeve 6 and is free torotate. The sleeve 6, which is integral with a support frame 7.

The support frame 7 is fastened to an arm 8, which extends, in asubstantially radial position, from a bar 10, which adjusts the positionof the nozzles 4.

The adjustment bar 10 is rotated, from outside the coating pan 1, by ahandwheel 11, as will be explained later.

The adjustment bar 10 passes through a tube 12, whose axis is parallelto the bar 10 and to the axis of the coating pan 1, and protrudes froman end of the coating pan 1, in the region of the front surface of theopening 3.

Outside of the coating pan 1, the tube 12 is fastened to a supportcolumn 14 by a flange 13.

The other end of the tube 12, situated inside the coating pan 1,supports a member 15, which positions the group of spraying nozzles 4.

The positioning member 15 includes substantially a lever mechanismformed by first lever 16 and a second lever 17, hinged to each other bymeans of a pin 18.

The first lever 16 is hinged to an annular disc 19 fixed to the tube 12,while the second lever 17 is integral with the shaft 5 of the sprayingnozzles 4 (FIG. 2a).

As seen in detail in FIGS. 3a, 3 b, the handwheel 11 is fastened to atubular hub 21, which is slidingly fitted, by a bush 22, to an inletshaft 23 of a reducer unit 24.

The hub 21 is coupled to the reducer unit 24 in the region of aprismatic head 25 of the inlet shaft 23.

At the outlet, the reducer unit 24 operates the bar 10 adjusting theposition of the spraying nozzles 4.

The bush 22 is fastened to a ring 26, which is fixed to the front partof the hub 21 and acts as abutment for one end of a helical spring 127.

The other end of the helical spring 127 pushes the prismatic head 25.

The handwheel 11 has also an annulus 27 surrounding the hub 21, with apin 28 protruding from the annulus.

The pin 28 can engage with one of a plurality of equidistant holes madein a disc 29 fastened to the flange 13 of the tube 12.

Therefore, when in a rest position, seen in FIG. 3a, the handwheelcannot rotate because the pin 28 is engaged with a hole of themotionless disc 29.

In order to rotate the handwheel 11, it is necessary to pull it, so asto make it slide axially against the action of the spring 127, until thepin 28 disengages from the hole 29 a of the disc 29 (see FIG. 3b).

In this disengaged position, it is possible to rotate the handwheel 11through a desired angle, thus rotating the inlet shaft 23 of the reducerunit 24 and consequently, the bar 10 of the device moving the nozzles 4.

Then, the handwheel 11 is brought back to the locked position, with thepin 28 engaged with a corresponding hole of the disc 29, due to thebackward elastic reaction of the spring 127.

A transducer 30 is joined to the inlet shaft 23 to control the rotationimposed by the handwheel 11.

The proposed device includes also a sensor 9, which detects in real timethe distance of the granular articles 2 from the free surface 20.

Therefore, the proposed device allows to move the group of sprayingnozzles 4 from outside of the coating pan 1.

Actually, the rotation of the handwheel 11 drives the bar 10 intorotation.

The bar 10 carries the arm 8, on which the frame 7 supporting thenozzles 4 is mounted.

The movement of the support frame 7 determines the reciprocal rotationof the levers 16, 17 of the positioning member 15, as seen in FIG. 2a,where the reference numeral 4 a indicates a different position of thespraying nozzles 4 and the numeral 15 a indicates the position assumedcorrespondingly by the lever mechanism of the positioning member 15.

Actually, one end of the first lever 16 is hinged to a fixed point,while the second lever 17 is driven to follow the movement of thesupport frame 7.

The reciprocal rotation of the levers 16, 17 of the positioning member15 determines a corresponding rotation of the shaft 5 of the sprayingnozzles 4, which compensates for the opposite rotation determined by themovement of the arm 8, so as to maintain substantially the sameorientation of the spraying nozzles 4 with respect to the free surface20 of the mass of articles 2 to be treated.

Practically, by acting on the handwheel 11, it is possible to drive thespraying nozzles 4 from outside of the coating pan 1, during the coatingof the granular articles 2, so as to maintain the spraying nozzles 4 ata constant distance from the free surface 20 of the articles 2 when thevolume of the mass of articles 2 changes. This distance is detected inreal time by the sensor 9.

At the same time, the lever mechanism of the positioning member 15changes automatically the orientation of the spraying nozzles 4, so asto maintain constant the orientation thereof with respect to the freesurface 20 of the mass of granular articles 2, in particularperpendicular to the free surface 20.

It is to be noted that, after the arm 8 carrying the frame 7 of thespraying nozzles 4 has performed rotation of a certain angle, thespraying nozzles 4 are turned over, as indicated with 4 b in FIG. 2a.

The position assumed by the positioning member 15 is indicated with 15 bin the same Figure.

This allows to position the group of spraying nozzles 4 in such a waythat they can be removed from the coating pan 1.

Otherwise, the spraying nozzles 4 can be moved automatically by aspecial motor 31, mounted coaxially with the bar 10, as schematicallyshown in FIG. 1.

The motor 31 is controlled by known automatic programmable means,operated by the signal of the sensor 9.

Consequently, the proposed device allows to obtain best workingconditions of the spraying nozzles inside a coating pan during coatingof the granular articles, maintaining constant the distance between thespraying nozzles and the free surface of the mass of articles, orchanging this distance in a programmed way in relation to differentcharacteristics of the liquid substances to be sprayed.

What is claimed is:
 1. A device for moving and orienting sprayingnozzles in a coating pan, the coating pan including: a rotating drum (1)rotated on a first rotation axis for mixing a predetermined mass ofarticles (2) being coated, said mass of articles defining a freesurface; and a group of spraying nozzles (4) situated inside saidrotating drum for spraying a liquid mixture for coating said articles(2); said device being characterized by: a bar (10) supported insidesaid rotating drum (1) and protruding partially outside said rotatingdrum (1); a support frame (7), fastened to said bar (10) and locatedinside said rotating drum (1); a shaft (5) rotatably supported by saidsupport frame (7), said shaft (5) being free to rotate on a secondrotation axis parallel to said first rotation axis of said rotating drum(1); a plurality of spraying nozzles (4) carried, arranged in a line, bysaid shaft (5) at a selected distance from said mass of articles (2)being treated with a selected orientation with respect to said freesurface (20) of the mass of articles (2); a positioning member (15)having a lever mechanism (16,17) connected to said shaft (5) forchanging inclination of said spraying nozzles (4) and maintainingconstant the orientation of said spraying nozzles (4) with respect tosaid free surface (20) of the mass of articles (2); said bar (10) beingrotated to adjust said distance between said spraying nozzles (4) andsaid free surface (20) of said mass of articles (2) being treated.
 2. Adevice, according to claim 1, further including a sensor (9) aimed atdetecting, in real time, the distance between said spraying nozzles (4)and the free surface (20) of said mass of granular articles (2).
 3. Adevice, according to claim 1, wherein said lever mechanism (16,17) ofthe positioning member (15) includes a first lever (16) hinged at oneend to a fixed point and a second lever (17) hinged at one end to saidfirst lever (16) and at the other end, integral with said shaft (5) ofthe spraying nozzles (4).
 4. A device, according to claim 1, whereinsaid bar (10) is rotated by a motor (31), controlled by a sensor (9),which detects, in real time, the distance between said spraying nozzles(4) and the free surface (20) of said mass of granular articles (2). 5.A device, according to claim 1, wherein said bar (19) is rotated by ahandwheel (11) situated outside said coating pan (1).
 6. A device,according to claim 5, wherein said handwheel (11) is equipped with atubular hub (21), which is slidingly mounted on an inlet shaft (23) of areducer unit (24), so as to transmit motion to said bar (10), said hub(21) being coupled to said inlet shaft (23) by prismatic means (25), soas to move between a locked position and an axial pulling position, inwhich the handwheel (11) is allowed to rotate, said locked positionbeing determined by engaging of coupling means (28), carried by saidhandwheel (11), with corresponding holes made in a motionless disc, dueto the push of elastic means (127), and said axial pulling positionbeing determined by disengagement of the coupling means (28) against theaction of said elastic means (127).
 7. A device, according to claim 1,wherein said support frame (7) is fastened in an adjustable position, toan arm (8), which extends, in a substantially radial position, from saidbar (10) adjusting the nozzles (4) position.
 8. A device, according toclaim 1, wherein said bar (10) for adjusting the nozzles (4) positionpasses through a motionless tube (12), whose axis is parallel to theaxis of the coating pan (1), and protrudes from one end of said coatingpan (1), said tube (12) acting as a support for said positioning member(15) inside said coating pan (1).